1. Field of the Invention
This invention relates to a data recording/reproducing apparatus such as a magnetic disk apparatus, and more particularly to a data recording/reproducing apparatus having a carriage lock mechanism using a magnet.
2. Description of the Related Art
In a magnetic disk apparatus employing the CSS (Contact Start and Stop) method, a CSS zone, i.e., an area other than the data zone, is formed in the innermost portion of a disk (recording medium), to protect the surface of the disk from damage. The magnetic head is placed in contact with the CSS zone when a power source of the magnetic disk apparatus is turned off. The magnetic head is included in a carriage and moves over the disk in accordance with the movement of the carriage. When the power source of the magnetic disk apparatus is turned on and the disk is rotated, the magnetic head is flown from the CSS zone, and then toward the outer portion of the disk, i.e., the data zone.
When the power source of the magnetic disk apparatus is turned off, if the apparatus vibrates, thereby moving the carriage, the magnetic head in contact with the CSS zone may be moved, resulting in damage to the surface of the disk. To prevent this, a lock mechanism for locking the carriage is provided in the magnetic disk apparatus, so that the carriage including the magnetic head on the CSS zone is not easily moved.
For this purpose, a carriage lock mechanism which locks the carriage by utilizing magnetic force of a magnet may be used. This carriage lock mechanism locks the carriage including the magnetic head on the CSS zone by the magnetic force of, for example, the magnet of a voice coil motor (VCM) for moving the carriage. In the carriage lock mechanism, when the magnetic head is moved from the CSS zone to the data zone (this movement is hereinafter referred to as an initial seek operation), the force which releases the carriage from the locked state is applied to the carriage.
In a conventional apparatus, a constant current necessary to generate force for releasing the carriage from its locked state is continuously supplied to the voice coil motor during an initial seek operation. However, as shown in FIG. 1, since the magnetic force (hereinafter referred to as offset force) does not affect the carriage which includes the magnetic head on the data zone relatively large force is applied to the carriage in the direction toward the outer portion of the disk. As a result, the magnetic head cannot detect servo data in the data zone, and may run out of control. Therefore, since the magnetic head and the surface of the disk may be damaged, data recorded on the disk will be destroyed.
Under the circumstances, it is demanded to develop a data recording/reproducing apparatus wherein the carriage is released from the locked state at an initial seek operation without causing the magnetic head to run out of control.